Nuclear transition between the conjunction cells of Phaeodactylum tricornutum Bohlin (Bacillariophyta)

Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production. Its reproduction has profound significance in the life cycle; however, the nuclear behavior during its sexual reproduction was not clear. In this study, we observed the nuclear transition and determined its correlation with cell conjunction. It was found that two cells jointed at their apices first and swung and aligned each other immediately, and nucleus from one cell was able to transfer into another one during cell conjugation. The cell pairs conjugated for nuclear transition were different from those formed in mitosis in hypovalve thickness and cellular arrangement. Our findings proved the existence of sexual reproduction in P. tricornutum.     

不同无机氮浓度下中肋骨条藻和三角褐指藻生长对生长环境pH的影响

海洋酸化是当前一个严重的环境问题,而海水pH的变化与微藻生长时对溶解无机碳的吸收有关。在室内条件下采用生理生态学方法,研究中肋骨条藻Skeletonema costatum和三角褐指藻Phaeodactylum tricornutum在不同无机氮水平下生长到最大生物量时培养液pH的变化。结果表明,培养液无机氮浓度从10μmol.L-1上升到200μmol.L-1过程中,2种微藻的叶绿素浓度和最终pH均呈上升趋势。培养液pH的增加量与无机氮的消耗量呈正相关关系,培养液pH的增加量与溶解无机碳的消耗量也呈正相关关系。     

光-暗循环中三角褐指藻和具齿原甲藻快速光曲线的变化

利用脉冲振幅调制叶绿素荧光仪研究了光一暗循环中三角褐指藻Phaeodactylum tricornutum和具齿原甲藻Prorocentrum dentatum的快速光曲线变化。在光一暗循环中2种藻的快速光曲线呈周期性变化,但具齿原甲藻的最大相对电子传递速率始终快于三角褐指藻,前者是后者的1．8—2．6倍。照光后三角褐指藻和具齿原甲藻的光合参数α和Pm迅速上升到最大值,在随后的光照期间α和Pm逐渐下降,经12h暗适应后恢复到初始值,呈明显的周期变化。这种变化可能受外界光强和生物节奏双重调节。光系统Ⅱ的有效量子产量随光合有效辐射（PAR）升高而下降,但在光照期间PAR较低时存有效在量子产量随PAR升高而升高的现象,这可能是由“状态转换”或叶绿体呼吸引起的。在光-暗循环中,2种藻的α均有较高的变异系数,说明利用固定光合参数计算初级生产力得到的误差中α的贡献较大。     

几种单胞藻对婆罗异剑水蚤群体增殖的影响

研究了不同浓度的三角褐指藻（Ｐｈａｅｏｄａｃｔｙｌｕｍ　ｔｒｉｃｏｒｎｕｔｕｍ）和不同种单胞藻单独喂养 及混合喂养对婆罗异剑水蚤 Ａｐｏｃｙｃｌｏｐｓ　ｂｏｒｎｅｏｅｎｓｉｓ群体增殖的影响。经１０ｄ的培养,初步得 出：三角褐指藻对婆罗异剑水蚤适宜的浓度为２０×１０~４～５０×１０~４ｃｅｌｌ／ｍｌ;在４种单胞藻中, 等鞭金藻（Ｉｓｏｃｈｒｙｓｉｓ　ｓｐ．）效果最好,扁藻（Ｐｌａｔｙｍｏｎａｓ　ｈｅｌｇｏｌａｎｄｉｃａ）次之,小球藻（Ｃｈｌｏｒｅｌｌａ　ｓｐ．）最 差;几种单胞藻混合喂养婆罗异剑水蚤,其群体增殖效果总体上比单种藻类喂养来得显著。 还就不同浓度的藻类及不同种藻类单独或混合喂养对婆罗异剑水蚤群体增殖的影响进行 讨论。     

化学诱变剂在实验海洋食物链中的流动以及遗传毒性的检测——镉在褐指藻→中国对虾→欧氏六线鱼实验食物链中的传递

于1989年3月—1989年9月,利用极谱测定法研究了无机诱变剂Cd在3级实验食物(链从褐指藻经中国对虾至欧氏六线鱼)中的传递,并对积累Cd的中国对虾和欧氏六线鱼肌肉和内脏灰样进行了紫露草微核测定。结果表明,Cd浓度在传递中依次减少;经过6d喂食,Cd从褐指藻到中国对虾的传递比例为66.6％;经过7d喂食,Cd从中国对虾到欧氏六线鱼的传递比例为29.9％。t测验发现,处理组对虾内脏灰样与肌肉灰样之间诱变性差异显著(P<0.01);处理组与对照组对虾内脏灰样之间的诱变性差异亦显著(P<0.01)。     

影响三角褐指藻生长的生态因子间关系及其调节效应

运用 3× 3× 2析因试验 ,研究NO3 N质量浓度、光照强度和温度间的相互关系及其对三角褐指藻 (Phaeodactylumtricornutum)生长的调节效应。结果表明 :NO3 N以抛物线方式控制藻的生长 ,光照强度主要影响藻的指数生长期 ,对稳定态细胞密度影响减弱 ,温度升高有助于生长。当温度为 2 0℃ ,NO3 N质量浓度分别为 14 .7和 14 .6mg/L ,光照强度分别为5 36 4 .0和 4 0 35 .4lx时 ,藻相对生长率和细胞密度达到最大值 ,分别为 0 .6 5 15d-1和10 10 .7× 10 4/mL。光肥效应、温肥效应和光温效应存在于藻类生长过程 ,并且起协调作用。增产效应随NO3 N含量增加而减少 ,随光照强度和温度的升高而增加     

镉在褐指藻～海湾扇贝食物链中的传递以及遗传毒性的检测

为了探究化学诱变剂镉在海洋食物链中的传递规律及其与人类健康的关系,作者设计了从海洋浮游藻类——褐指藻(Phaeodactylum tricornutum Bohlin)～海湾扇贝(Argopecten irradians Lamarck)的实验室食物链,采用极谱分析方法研究了镉的传递,并对贝肉(软体组织)灰样进行了紫露草微核(Trad-MCN)测定,结果:(1)经过6d的传递实验,处理组与对照组贝肉中镉的浓度均未超过对应组褐指藻中镉的浓度;经过这条食物链的传递,镉的浓度减少。(2)通过t测验发现,两个高浓度处理组与对照组贝肉灰样之间的诱变性差异显著(P<0.001与P<0.005)。t值的大小与镉的浓度具有一致性关系,说明镉的浓度越大,诱变性越强。     

三角褐指藻Δ5去饱和酶基因的原核表达

Δ5脂肪酸去饱和酶(Δ5fatty acid desaturase)是合成花生四烯酸(AA)和EPA的关键酶。为了构建三角褐指藻Δ5脂肪酸去饱和酶基因(简称D5)的原核表达重组质粒,并实现在E.coli BL21(DE3)中的表达。本研究根据GenBank中三角褐指藻Δ5脂肪酸去饱和酶基因序列,设计引物,扩增该基因并插入到pET28a中,测序鉴定后,转化E.coli BL21(DE3)感受态细胞,IPTG诱导表达,SDS-PAGE分析表达产物。结果表明pET28a-D5构建成功,IPTG能诱导D5特异性表达。     

Molecular insights into the circadian clock in marine diatoms

The circadian clock is a fundamental endogenous mechanism of adaptation that coordinates the physiology and behavior of most organisms with diel variations in the external environment to maintain temporal homeostasis. Diatoms are the major primary producers in the ocean. However, little is known about the circadian clock in marine diatoms compared with other organisms. Here, we investigated circadian clock genes, their expression patterns, and responses to environmental stimuli such as light, nitrogen and phosphorus in two marine diatoms, Skeletonema costatum and Phaeodactylum tricornutum, using a combination of qRT-PCR and bioinformatic analysis. We identified 17 and 18 circadian clock genes in P. tricornutum and S. costatum, respectively. Despite significant evolutionary differences, these genes were similar to those of the higher plant Arabidopsis. We also established a molecular model for the marine diatom circadian clock comprising an input pathway, core oscillator, output pathway, and valve effector. Notably, the expression patterns of core clock genes (circadian clock associated 1 (CCA1), late elongated hypocotyl (LHY) and timing of cab 1 (TOC1)) in both species differed from those of terrestrial plants. Furthermore, the expression of these genes was influenced by variations in ambient light, nitrogen and phosphorus availability. Although marine diatoms and higher plants share common circadian clock components, their clock genes have diverged throughout evolution, likely as a result of adapting to contrasting environments.